container.training/slides/kube/whatsnext.md

Stateful services (databases etc.)

• As a first step, it is wiser to keep stateful services outside of the cluster

• Exposing them to pods can be done with multiple solutions:

  • ExternalName services
    (redis.blue.svc.cluster.local will be a CNAME record)

  • ClusterIP services with explicit Endpoints
    (instead of letting Kubernetes generate the endpoints from a selector)

  • Ambassador services
    (application-level proxies that can provide credentials injection and more)

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Stateful services (second take)

• If you really want to host stateful services on Kubernetes, you can look into:

  • volumes (to carry persistent data)

  • storage plugins

  • persistent volume claims (to ask for specific volume characteristics)

  • stateful sets (pods that are not ephemeral)

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HTTP traffic handling

• Services are layer 4 constructs

• HTTP is a layer 7 protocol

• It is handled by ingresses (a different resource kind)

• Ingresses allow:

  • virtual host routing
  • session stickiness
  • URI mapping
  • and much more!

• Check out e.g. Træfik

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Logging and metrics

• Logging is delegated to the container engine

• Metrics are typically handled with Prometheus

  (Heapster is a popular add-on)

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Managing the configuration of our applications

• Two constructs are particularly useful: secrets and config maps

• They allow to expose arbitrary information to our containers

• Avoid storing configuration in container images

  (There are some exceptions to that rule, but it's generally a Bad Idea)

• Never store sensitive information in container images

  (It's the container equivalent of the password on a post-it note on your screen)

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Managing stack deployments

• The best deployment tool will vary, depending on:

  • the size and complexity of your stack(s)
  • how often you change it (i.e. add/remove components)
  • the size and skills of your team

• A few examples:

  • shell scripts invoking kubectl
  • YAML resources descriptions committed to a repo
  • Helm (~package manager)
  • Spinnaker (Netflix' CD platform)
  • Brigade (event-driven scripting; no YAML)

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Cluster federation

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Sorry Star Trek fans, this is not the federation you're looking for!

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(If I add "Your cluster is in another federation" I might get a 3rd fandom wincing!)

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Cluster federation

• Kubernetes master operation relies on etcd

• etcd uses the Raft protocol

• Raft recommends low latency between nodes

• What if our cluster spreads to multiple regions?

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• Break it down in local clusters

• Regroup them in a cluster federation

• Synchronize resources across clusters

• Discover resources across clusters